The present disclosure relates to integrated circuit (IC) structures in complementary metal oxide semiconductor (CMOS) circuits. More particularly, the present disclosure relates to on-chip decoupling capacitor structures having trench decoupling capacitors integrated with a passive decoupling capacitor formed in the back-end-of-line (BEOL) wiring of the circuit.
One goal for semiconductor designers is to design highly reliable, super high performance CMOS circuits with ever increasing functionality requirements, while consuming the lowest possible power. This becomes more important for low power battery operated devices where battery-operating lifetime is crucial.
In this mode of operation, circuit designers face a number of challenges to insure high signal integrity within the chip and the semiconductor package. Simultaneous switching through the input and output (I/O) pins give to current “noise” spike within a specified time, severely degrading the signal integrity. The signal integrity is jeopardized mainly by the “noise” on the power and ground planes due to the capacitance coupling between power and signal lines.
To insure the system reliability against such deleterious effects, decoupling capacitors, known as DECAPS, are added to the power and ground planes to provide an AC ground for the noise and provide a stable DC voltage.
One current methodology for embedding a DECAP on a microprocessor is to form a trench-type capacitor that is made directly in the silicon wafer and the sidewalls of the trench are used for the capacitor dielectric. Such trench-type capacitors offer higher capacitance densities over the planar capacitors and lower leakage current. Unfortunately, the area density of deep trench DECAPS is limited by the thickness of the substrate.
Another current methodology for embedding a DECAP on a microprocessor is to form a passive decoupling capacitor on the surface of the silicon wafer. Unfortunately, such wire-based DECAPS occupy chip volume that is valuable for wiring of other devices to the microprocessor.
Accordingly, there is a continuing need in the integrated circuit industry for increased decoupling capacitance beyond that currently available.